This invention is related to mechanical interlocks between a pair of vertically mounted circuit breakers for preventing one of the circuit breakers from closing when the other circuit breaker is closed.
The control of electrical systems including such devices as reversible motors and multispeed motors usually utilizes a circuit breaker for each motor function. A typical circuit includes, for example, a separate manual button for each circuit breaker for the forward and reverse directions of the motor and for each speed of a multispeed motor. For example, for a reversing motor the control circuit involved for the forward speed and for the reverse speed would be electrically interlocked such that both circuits could not simultaneously be energized. Notwithstanding such precautions, however, it sometimes occurs due to inadvertence or other reasons that both control circuits (i.e. forward and reverse) are actuated simultaneously and thereby cause incorrect phase-to-phase line connections. Another typical circuit involves transfer circuits with normal and emergency sources for which one circuit breaker must be prevented from closing when the other breaker is closed. Thus, there is a need for a mechanical as well as electrical interlocking between the two circuit breakers.
Various interlock devices had been provided for overcoming the problem of simultaneous actuation of circuit interrupters. However, most of such interlocks have not been completely satisfactory for various reasons. An example of a mechanical interlock is set forth in U.S. Pat. No. 4,286,242, issued Aug. 25, 1981 entitled "Mechanical Interlock for Low Voltage Circuit Breaker" and assigned to the assignee of the present invention. However one disadvantage of this interlock is that it is primarily utilized for side-by-side mounting of circuit breakers and is not readily adaptable for vertically mounted circuit breakers now found in most multi-speed or reversing motor applications.